Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Oct. 31, 2020	Jan. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Aggregate Fair Value	$ 156,337	$ 116,833
Current marketable securities	156,300
Noncurrent marketable securities	3,100
Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	563,867	244,728
Unrealized Gains	0	22
Unrealized Losses	(16)	0
Aggregate Fair Value	563,851	244,750
Cash and Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	404,432	127,917
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	404,432	127,917
Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	156,351	116,811
Unrealized Gains	0	22
Unrealized Losses	(14)	0
Aggregate Fair Value	156,337	116,833
Other Noncurrent Assets
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,084
Unrealized Gains	0
Unrealized Losses	(2)
Aggregate Fair Value	3,082
Money market funds \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	356,737	92,272
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	356,737	92,272
U.S. government and agency securities \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	114,646	115,412
Unrealized Gains	0	13
Unrealized Losses	(5)	0
Aggregate Fair Value	114,641	115,425
Commercial paper \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	62,166	31,379
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	62,166	31,379
Corporate notes and bonds \| Cash, Cash Equivalents and Marketable Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	30,318	5,665
Unrealized Gains	0	9
Unrealized Losses	(11)	0
Aggregate Fair Value	$ 30,307	$ 5,674

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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